The goal of this project is to use molecular genetic techniques to study the structure and function of mammalian bombesin receptors. We plan to accomplish this objective by first obtaining cDNA clone for the murine bombesin receptor found on Swiss 3T3 fibroblasts in relatively high numbers. The cDNA will be sequenced to determine the predicted amino acid sequence and general structural features of the receptor. Specific antisera will be generated against synthetic peptides to allow further characterization of the receptor protein. This cDNA clone can then be used in site-specific mutagenesis studies where the effects of structural perturbations can be examined after expression of the mutant receptors in Xenopus oocytes and DNA-mediated transfection into murine fibroblasts which do not normally express the receptor. Genomic clones will be isolated to examine the gene structure and promoter region. The cDNA coding domain will be used as a low-stringency probe to screen cDNA libraries from appropriate sources for other distinct but structurally related bombesin receptor cDNA cones, including a distinct subtype found on esophageal smooth muscle and in the olfactory bulb of the brain.